Bernadette -

I soooo feel your pain. Both of my kids had lice a year and a half ago. Alyssa worse than Nicholas, but that's because his hair was short and hers was long. I swear they got it at WDW, trying on those hats, or the Jedi Training thing where they put that robe/cape on their head. I don't remember any welts, but the lice are brown and if they are small it is very hard to see them. As they mature they get bigger, and they move FAST. If there are egg sacs, those are white, and they attach themselves to the shaft of the hair, about 1/2-1 inch from the scalp. The difference between the white sac and a white flake of scalp is that the sac will need to be scraped from the hair shaft with a fingernail. It won't move by simply picking or blowing it out. I tore the house apart, vacuumed EVERYTHING. Put ALL sofa and bed (got them new bed ones) pillows/stuffed animals in bags for weeks to kill anything that might have been brewing. Then every night for 3 weeks we went through a regimen of combing their hair, bit by bit, with a lice pick. It was HORRIBLE. Thank GOD I didn't get it. Lot's of prayers that Emma doesn't have it. If you have any questions feel free to PM me.
ETA - Have you noticed her scratching her head a lot? That is what drew my attention to Alyssa, and when I looked, I found it. She did have scratches on her scalp from itching so much.